Method and means for producing a ceramic or metallic product for sintering

ABSTRACT

A device including an injection molding tool for use once or a few times for producing a sinterable ceramic and/or metallic product. The device includes at least one first tool part. At least one second tool part is combinable with the at least one first tool part to form a molding space for the product. The second tool part is produced using a wet composition and is made of a readily worked and form-stable material containing pores and admixed heat-conducting particles. A wet composition-enclosing member can engage the first tool part during the production of the second tool part. A unit can be connected to the at least one second tool part and can be arranged with the at least one first tool part for absorbing internal lateral displacement forces arising during squeezing or injection of an injection molding composition. The injection molding tool is adapted to receive an injection molding composition containing a ceramic and/or metallic powder that is introduced into the molding tool with low or medium pressure for forming the product. The pores and the admixed heat-conducting particles conduct away heat generated during the molding and gas trapped in the molding space. The pores also provide a well-balanced porosity for effecting conduction of the gas and, together with a flexibility in the solidified injection molding composition, permit the product to be separated from the tool parts without braking.

This application is a U.S. National Application of PCT/SE96/00819, filedJun. 24, 1996.

TECHNICAL FIELD

The present invention relates, to among other things, a process forproducing a sinterable ceramic or metallic body, which can also have anindividual and distinctive shape and, for example, consists of a dentalbridge shell. The production is executed using a tool/molding tool whichcan be assembled from two or more tool parts and whose molding spacecorresponds to the shape of the body. The invention also relates to adevice or tool for producing the sinterable ceramic or metallic productor ceramic prosthesis (metallic prosthesis). Furthermore, the inventionrelates to a process for producing a shell for a metallic or ceramicproduct or a ceramic prosthesis (metallic prosthesis) which is designedto be anchorable to a base which has been prepared in the human bodyand, for example, includes or consists of an implant, tooth remnant(s),etc. In the process, use is made of a tool having a molding space forthe shell and of first and second models of the base and the shell,respectively. The invention also relates to an injection molding toolfor the product or prosthesis. The invention also relates to a processfor producing an injection molding composition, which comprises apolymer melt and/or wax, melt (binding agent) and powder particles mixedinto this melt. The composition is intended to be squeezed or pressed,in the melted state, into one or more spaces in an injection moldingtool to achieve a sinterable body which is formed when the compositionis in solidified form and which preferably has an individual and/orcomplex shape. In addition, the invention relates to a powder for aninjection molding composition which, in the melted state, can besqueezed or injected under low or medium pressure, by which in this caseis meant 1-200 bar, into one or more molding spaces in an injectionmolding tool for the purpose of forming a sinterable solidified bodywhich preferably has an individual and/or complex shape. Finally, theinvention relates to an injection molding composition for forming, in atool, a sinterable body which preferably has an individual and/orcomplex shape. The composition comprises a sinterable powder which hasbeen treated with a hydrophobic agent and can be mixed into a melt ofbinding agent, for example paraffin wax and/or polyethylene. Theinvention can also be used for making products in metal/hard metal, withuse being made of metal powder, for example titanium powder, which ismolded and sintered to the desired density.

BACKGROUND OF THE INVENTION

The production of ceramic products or ceramic prostheses is very wellknown. Thus, for example, it is known to make use of die castingemploying a tool which has a porous tool part through whose poressolvent, which has been released, is conducted away during the castingprocess. When producing dental bridges, for example, it is already knownto use models of jawbone impressions and dental bridge shapes forproducing dental bridge shells, which are to be coated with additionalmaterial for aesthetic shaping. It is also known to produce tools andtool parts to which the shape of the product or prosthesis can betransferred using a copying technique, after which the tool or tool partis used for spark machining a workpiece to form the product orprosthesis.

It is also well known to produce different types of wet compositionscontaining solvents and plaster and to use these in connection withmaking ceramic products in the form of coffee pots, lavatory seats,exhaust ports for internal combustion engines, etc. In this context, itis known to propose injection molding compositions which include ceramicpowder or metallic or alloy powder which can be mixed into the melt ofbinding agent in the form of wax, polymers, etc. In connection withthis, well-known technology proposes the use of dry crushing processes,dispersing agents, etc.

The body/product/prosthesis which is referred to above and which isproduced using the present invention must be sinterable. The sinteringconfers the desired hardness on the body during the course of a certaindegree of shrinkage. Such sintering is well known and is not part of thesubject-matter of the present invention.

In connection with production of the product, there is a need for atechnically simple tool for producing one or a few products, for examplewhen making dental products, manufacturing prototypes, making productsin small series, etc. In this context, the tool must have a technicalconstruction, which permits economic use. The sole product, or the fewproducts, must themselves carry the tool costs, which, in the case ofdental bridge production, for example, implies a tool cost of only 20-30SEK/product, calculated at present-day prices. The use of present-daytechnology and the manufacture of tool parts in, for example, high speedsteel and the like results in a cost which is many times greater andwhich makes it impossible to produce the tools as disposable tools. Thisis one of the problems the invention is intended to solve.

In, for example, the production of dental products having individual andoften complicated shapes, for example dental bridge shells, there isneed to obtain a sinterable body/dental bridge, while retaining the highdemands for fit which are placed on this body/dental bridge, by means ofa single treatment step (molding). For example, it is difficult, whencasting ceramic bodies, to prevent these bodies from buckling, whichresults in poor fitting shape. In accordance with the present invention,these problems are solved by special tool construction, tool productionand a specially indicated injection molding composition.

Especially in the production of dental bridges, there is a generalrequirement for simplified methods for producing individually shapedproducts/bodies with a high degree of precision. The invention alsoprovides solutions to this problem and makes it possible to create, inone and the same tool assembly, the underside and external contours of abody/dental bridge, which can extend between two or moreteeth/attachment points in the dentine. In doing this, it is possible toavoid previous problems involved in creating bodies in severalmanufacturing steps, in which the external shape is transferred via acopying function is and the internal shape is produced by means of sparkmachining using a tool(s) to which the internal shape has previouslybeen transferred by means of copying.

In connection with the injection molding of a product having acomplicated shape, there is a need for heat to be conducted away in anefficient manner and for preventing distortion of the result by aircushion(s) which is/are trapped in the molding space. These problems,too, are solved by the invention, which proposes a specific heat-removalfunction using a heat conducting metal or alloy particles of specificquantity which are mixed into a tool part and which ensure that heat isconducted away in an appropriate manner. Thus, a well-balanced porosityin the tool part guarantees that air is removed in an appropriate mannerfrom the molding space during the molding of the product. A porosity,which is too low, does not provide sufficient removal of air, and aporosity which is too high, with pore channels which are too large,results in the injection molding composition flowing out into the toolpart.

When producing a tool part as described above, a wet composition is usedwhose solvent (water) is driven off by drying under ambient conditionsor at an elevated temperature.

The demand placed on the material in the tool part, which is producedusing the wet composition, is that it exhibits the properties, which arerequired as regards the injection molding and other aspects of theproduction. Thus, for example, the composition must be easy to shape orpour and, in the solidified state, exhibit shape-stability propertieswithin given areas. It must be possible for the chemical reaction totake place at room temperature and it must be possible to regulate theporosity by means of pressure and temperature. The invention also solvesthese problems and recommends, as an example, that the modulus ofelasticity should be>1 GPa in the solidified material.

There is a need, in this connection, to obtain a coherent, sinterablebody as the result of the injection molding. In addition, it must beeasy to separate the body from the tool part, i.e. the material in thebody must exhibit a certain flexibility so that the injection-moldedbody does not break when being separated from the tool part or toolparts. This places demands on the make-up of the injection moldingcomposition, which, in addition, must be such that confluence orchemical reaction with the tool part produced from the wet compositiondoes not take place. The invention also solves this problem.

In the production of the injection molding composition and the powderfor this composition, it is essential that the powder agglomerate can bebroken up and that preparation of the powder takes place in such a waythat optimal homogeneity of the composition, without contamination, canbe achieved using a limited number of process steps. It must be possibleto hydrophobicize the powder surfaces efficiently by removing the excessof absorbed water. The dry matter content of the powder before it ismixed into the polymer melt and/or wax melt must be high, and it isadvantageous if the energy consumption can be held down during thecourse of the admixing. The invention also solves these problems andproposes an effective preparation process prior to the admixture withthe wax and/or the polymer.

SUMMARY OF THE INVENTION

The present invention is characterized in that at least one tool part isproduced from a wet composition which comprises solvent, heat conductingparticles and material which is easy to work and whose shape is stablein solidified form. The material is caused to solidify in a bindingfunction (for example chemical reaction), after which the solvent isdriven off by drying and a pore channel system is thereby formed in thesolidified material. During the solidification, a part of the shape ofthe body is transferred to the tool part or the solidified material. Theremaining shape or shapes of the body is/are transferred to the othertool part(s). Sinterable injection molding composition is injected orsqueezed into the molding space using a low or medium compressionmolding pressure, by which, in this case, is meant a compression moldingpressure of between 1-200 bar. Heat which arises due to the injectionmolding composition which has been injected into the molding space isconducted away by means of the heat-conducting particles in thesolidified material. Gas or air which is trapped in the molding spaceduring the injection or the squeezing-in is conducted away through thepores in the solidified material.

An injection molding tool for carrying out the process is arranged withat least one tool part made of material which is readily worked andform-stable, examples of such material which may be mentioned in thiscontext being plaster, cement, aluminum phosphate-bound or sol-bound(so-called cold bound) ceramic mixtures, sintered porous metal/ceramicmixtures, etc. The material must contain pores and admixedheat-conducting particles which are to form a heat-removal network forthe heat. The tool part can be combined with one or more other toolparts in order to form one or more molding spaces for theproduct(s)/prosthesis (prostheses). The injection molding tool isarranged, in connection with the formation of the sinterable product orprosthesis, to receive an injection molding composition which issqueezed in using a low pressure or a medium pressure and which containsa sinterable ceramic powder or metallic powder. Heat, which is generatedduring the molding, and gas or air, which is trapped in the moldingspace, can be conducted away with the aid of the heat-conductingparticles and the pores, respectively.

The process for producing a shell for a ceramic product (metallicproduct) or ceramic prosthesis (metallic prosthesis) which uses a toolhaving a molding space for the shell and first and second models of abase which is allocated to the shell and the shell, respectively, isprincipally characterized in that the first model is applied to a toolpart and a first delimitation surface is thereby formed with the uppershape or upper surface of the base. The second model can be applied tothe first model from the outset or can be applied to the first model atthe time of or during the production. A member, which forms a moldingspace, is applied or arranged around at least the first model in thetool parts. A wet composition containing heat-removing particles isapplied to the molding space of the member so that the second model isenclosed by the wet composition. The latter is caused to solidify andthe solidified material is allocated the function of a second tool partwhich can cooperate with the first tool part, in which second tool partthe second delimitation surface of the molding space is formed by theouter shape or upper surface of the second model. After that, the firstand second tool parts are separated and the second model is removed. Thetool parts are brought together once again and means for forming theshell are injected or squeezed into the molding space which is therebyformed, with heat removal being effected by way of the heat-removingparticles.

An injection-molding tool for the process is characterized in that thefirst tool part is arranged to support a first model of the base (thejaw) which is to support the shell or equivalent dental product. In thiscontext, the base forms, by means of its upper parts, a firstdelimitation surface for the molding space. A second model, whichcorresponds to the shape of the shell or the dental product, can beapplied to the first model. The second tool part is formed out of orwith solidified wet composition which is applied at least around and toenclose the second model when the latter assumes its position on thefirst model. The second model can then be removed from the first modelin order to form the molding space. The shell can be produced by meansof injection molding composition which is injected or squeezed into themolding space which has thus been established. Heat removal during theinjection or squeezing-in is arranged to take place by way of theheat-conducting particles which are admixed with the solidified wetcomposition.

The process which was mentioned at the outset for producing an injectionmolding composition is principally characterized in that, before thepowder particles are mixed into the melt, the water which is absorbed bythe surfaces is driven off so that a high degree of drying is achieved.In this context, a high degree of drying is to be understood as meaningthat at most 5-20 percent of the original quantity of water remains.After that, the powder particle surfaces are coated with one or moreagents, for example stearic acid, by means of which agent or agents theparticle surfaces are hydrophobicized while, at the same time,deagglomerating and lubricating functions are implemented in theinjection molding composition both for the mutual separation (and betteradmixture) of the powder particles and for facilitating the introductionof the composition into the respective molding space using squeezing-inor injection members. After that, the powder having a high dry mattercontent can be mixed into the melt.

A powder for the injection molding composition has the powder particlesdried in order to obtain particle surfaces which are free fromphysically adsorbed water, in particular, and the particle surfaces arecoated with one or more agents, for example stearic acid. The agent hasa hydrophobicizing effect and brings about deagglomeration andlubricating functions which keep the particles apart and, respectively,facilitate injection and/or squeezing into each space of the spaces. Thepowder can be mixed with polymer and/or wax (for example paraffin wax)which contains binding-agent melt.

Hydrophobicization of the particle surfaces is preferably brought aboutmechanically by, for example, mixing the powder and hydrophobicizingadditives in a vessel in the presence of milling media on a drum bench.The size, quantity, hardness and form of the milling media can be chosenso that the milling effect is avoided. The task of the milling media isto effect abrasion of the particle surfaces, thereby creating reactivesurfaces for binding between the particles and the hydrophobicizingmedium which has been supplied. This binding is important for keepingthe particles apart during the mixing process. In other cases, millingmedia having a high degree of hardness and increased size and quantityare chosen in order, apart from bringing about the abovementionedeffect, also to bring about a simultaneous milling effect, i.e. decreasein the size of particles.

An injection molding composition according to the invention is alsocharacterized in that the proportion of wax in the solidified bodysubstantially exceeds the proportion of polyethylene, and in that thelatter proportion is only 1-10 percent volume of the former proportion.

By means of that which has been proposed above, technically efficientmanufacture of dental products (dental bridge shells) and prototypes canbe achieved employing tools which are used only once or just a fewtimes. The cost of producing the tools is minimal and very attractivefrom the industrial point of view. The processes involved in producingthe product can also be considerably simplified and do not require anyadditional measures arising from the use of the new type of tool. Theinjection molding composition can be arranged to be technically easy toprepare, using elements of is conventional production processes in whichthe preparation is characterized by technical simplicity and goodeconomy. The production of wet compositions for one or more tool parts(even all of them) is effected using techniques and material with whichthe dental technician or equivalent is thoroughly familiar. The removalof injection-molded, sinterable products from each tool part issimplified and ensured in a reliable and effective manner.

BRIEF DESCRIPTION OF THE DRAWINGS

A presently proposed embodiment of the process, devices and jointfillers/powders will be described below while at the same time referringto the attached drawings in which

FIG. 1 shows, in vertical section, an example of the construction of atool,

FIG. 2 shows the tool according to FIG. 1 in horizontal section,

FIG. 3 shows the tool according to FIGS. 1 and 2 in perspectiveobliquely from above, and

FIG. 4 shows a second embodiment of the tool in vertical section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

An injection-molding tool, designated by 1, is shown diagrammatically inFIG. 1. The tool comprises a lower tool part 2 and an upper tool part 3.The tool parts can be brought towards and away from each other, in thedirections of arrows 4, 5. The tool represents the injection molding ofa body 6 having a simple shape, for example a cylindrical body (bodyshape) which is provided with a bottom part. The body (body shape) isproduced in the mold 7 of the tool which is formed by the tool surfaces8, 9. A channel for injection molding composition is shown by 10. Thetool part 3, and, where appropriate, the part 2 as well, contain, intheir material, baked-in heat-conduction particles which can consist ofaluminum particles, alloy particles, bronze particles, etc. Theparticles form a network in the material for the purpose of effectingheat removal for heat which arises in the injection composition 11during the injection molding. A tube system 12 can be included as asupplement, with it being possible to circulate coolant in thedirections of arrows 13, 14 in accordance with FIG. 2.

FIG. 4 shows an example of a complicated shape which can be injectionmolded, consisting, for example, of a dental bridge shell 15 which hasto be applied to a base which is arranged in the human body and isformed from tooth remnants (implants, etc.), which tooth remnants arerepresented by 16 and 17 in FIG. 4. In the present case, the dentalbridge has to be attached to two tooth remnants 16 and 17 and extendover the space 18 for a tooth which has been removed. The tooth remnantsare symbolized or reproduced by a first model 19 which constitutes acopy of the tooth remnants (or equivalent). The shapes of the toothremnants have been transferred to the first model using a copyingprocess which can be of a known type. The first model is anchored in aknown manner to a first tool part 20. A second model 21 is applied tothe first model. The shape of the second model is produced in a knownmanner.

A member 22, which can have a cylindrical shape, is applied to the toolpart 20. The inner space of the member forms a space 23 for a wetcomposition 24, which is applied to the space 23 in viscous form. Thewet composition can be subjected to mechanical pressure using acompressing member 25 (disc). The wet composition contains 50 percent byweight of a metallic or alloy powder for providing the heat-removalfunction. The wet composition is solidified in the space by means of achemical reaction. During this reaction, the solvent (water) in the wetcomposition is driven off and forms pores (a porous wall) in tool part34. After the wet composition has solidified in the space, the toolparts 20 and 34 are separated and the model 21 is removed. With theremoval of the model 21, a molding space F is formed in which a firstdelimitation surface is constituted by the upper surface 26' of the base19 and a second delimitation surface 27 is constituted by the uppersurface 27' of the second model. The tool part is returned to theposition shown in FIG. 4 and the injection molding composition 28 ispressed or injected into the molding space F using an injection member29, which can be of a known type.

The injection pressure T can be between 1-200 bar. Compression of thewet composition 24 is effected using a tool part 29'. The tool parts 20and 34, and the member 22, are arranged to absorb lateral displacementforces f', f" which can arise due to the injection molding composition28 being injected, thereby guaranteeing precision in theinjection-molded product. Heat removal takes place, as described above,by means of the heat-removing particles 24a which are included in thesolidified wet composition. Air (gas) which is trapped in the moldingspace is conducted away via the porosity in the tool part 34 in thedirections of the arrows 30. The disc 25 does not seal the end surface24b of the upper tool part 34 tightly, and air can be conducted awayupwards, as is also the case for the removal of solvent from the wetcomposition.

Example I of an Injection Molding Composition Containing H₂ O₃ Powder

A ceramic powder, aluminum oxide, Alcoa SG 16, VSA, was treated inaccordance with the following procedure: 150 g of powder were weighed inand, in a first step, it was heat-treated at 150° C. for 3 hours in airin order to remove chemisorbed water; after that, the powder was left tocool in a desiccator. The loss of mass after this treatment was found tobe 0.53%. In a second step, the powder was hydrophobicized in anHD-polyethylene container, with 3 g (1.96% by weight) of finely powderedstearic acid (KEBO) being added, on a drum bench for 3 hours using 1 kgof aluminum oxide milling media. A melt was prepared from 30.0 g ofparaffin wax (KEBO, melting point: 62-64° C.) and 2.0 g of stearic acid,of identical quality as that described above, at a temperature of 120°C. An injection-moldable composition which was obtained by mixing thismelt and the hydrophobicized ceramic powder had a dry matter content of81.2% by weight, which corresponds to 50.1% by volume of aluminum oxide.A corresponding test was carried out using an identical Alcoa SG 16ceramic powder which was neither heat-treated nor hydrophobicized. Inthis case, all the stearic acid was added to the paraffin wax melt sothat the paraffin wax/stearic acid ratio corresponded to that in theabove case, i.e. approximately 6:1. An injection-moldable compositionwhich was obtained by mixing this melt and the untreated ceramic powderhad a dry matter content of 78.0% by weight, which corresponds to 45.2%by volume of aluminum oxide.

Example II of an Injection Molding Composition Containing Al₂ O₃ Powder

An injection molding composition was prepared having an Al₂ O₃ /MgOpowder content of 48% by volume: a mixture of 405 grams of Al₂ O₃ powder(Al6SG, ALCOA, USA) and 2 grams of MgO as sintering aid (MERCK, GERMANY)was heat-treated in a heating chamber at 300° C. for one hour, afterwhich the powder was hydrophobicized with 10 grams of stearic acid bybeing treated in an HD-polyethylene container together with Si₃ N₄spheres on a drum bench. The stearic [lacuna] at a temperature of 70° C.The composition was homogenized at 70° C. for two hours by means ofpropeller stirring.

The composition was poured into the filling trough, which had beenpreheated to 70° C., of a medium-pressure injection molder (MPIM) (GOCERAM HB, Sweden). Components were injection-molded using molding toolsas described in the examples below. The components were then placed on apowder bed of coarse-grained Al₂ O₃ for controlled elimination of theorganic additives in an RCE is (Rate-Controlled Extraction) BindingAgent Remover (GO CERAM HB, Sweden) in air. The components were thensintered (baked) to dense bodies at 1650° C. for one hour, and in anatmosphere of air, in a super kanthal kiln.

Example III of an Injection Molding Composition Containing Stainless 316Steel Powder

An injection molding composition was prepared having a steel powdercontent of 68% by volume: 1877 grams of gas-atomized, unfractionated 316steel powder (22 z,900 m, OSPREY, ENGLAND) were heat-treated in aheating chamber at 200° C. for one hour, after which the powder washydrophobicized with 15 grams of stearic acid. The stearic acid-coatedsteel powder was stirred into a melt of 80 grams of paraffin and 5 gramsof polyethylene, containing 17% by weight of ethylenebutyl acrylate, ata temperature of 75° C. The composition was homogenized at 75° C. fortwo hours by means of propeller stirring. Sedimentation experimentsshowed that the steel powder did not sediment, or sedimented much moreslowly, and had a considerably lower tendency to separate out from theparaffin than in experiments without the addition of polyethylene.

The composition was poured into the filling trough, which had beenpreheated to 75° C., of a medium pressure injection molder (MPIM) (GOCERAM HB, Sweden). Components were injection-molded using molding toolswhich were made as described below. The components were then placed in apowder bed of coarse-grained Al₂ O₃ for controlled elimination of theorganic additives in an RCE (Rate-Controlled Extraction) Binding AgentRemover (GO CERAM HB, Sweden) in hydrogen. The components were thensintered (burnt) to dense bodies at 1350° C. for two hours, in vacuo, ina graphite resistance kiln.

Examples of Injection Molding Tools (comparison with state of the art)

Three injection-molding tools were manufactured in different materials,with all the tools being of the same design as depicted above. One toolwas produced, by milling, entirely from black steel. For the other twotools, a plate was cast in acrylate plastic, with a metal cylinder beingapplied to the middle of the plate. The cylinder part, projecting upfrom the plastic, was covered with wax, thereby constituting the moldcavity. A slurry containing 70% by volume of hard plaster and 30% byvolume of fine-grained aluminum powder was poured over the plastic platetogether with the wax-covered metal cylinder. After solidification, theplaster was shaped and an inlet hole for the injection moldingcomposition was bored in it. In the same way, a molding tool half wasproduced from a slurry containing 70% by volume of cement and 30% byvolume of aluminum powder. The steel tool turned out to be ten timesmore expensive and took three times as long to manufacture as comparedwith the other two tools.

The tool part which is produced from a wet composition can also beprepared from ceramic/metallic powder mixtures containing a temporarybinding agent. The required properties are obtained by driving off thetemporary binding agent after the embedment and then baking the toolpart at a high temperature. This temperature is chosen so that the metalmelts and forms a network for efficient heat removal. At the same time,the co-sintered ceramic structure retains its shape and porousstructure. The metal and the ceramic can preferably be selected so thatthe ceramic is bound at contact points (by means of so-called neckformation) at the same time as the metal begins to melt and thus form aheat-conducting network through the pore channel structure. Thus, whatis characteristic is the production of a tool part from a wetcomposition without shrinkage and comprising metallic and ceramicmixtures.

The invention is not limited to the embodiment which has been shownabove as an example, and can be subjected to modifications within thescope of the subsequent patent claims and the inventive concept.

What is claimed is:
 1. A process for injection molding a dental product,the process comprising:utilizing a tool including a molding space forthe dental product, a first model for a base of the dental product and asecond model for a shell of the dental product; applying the first modelto a first tool part for forming a first delimitation surface with anupper surface of the first model; applying the second model to the firstmodel; arranging a member that forms a molding space around at least thefirst model; injecting a wet composition containing heat-conductingparticles into the molding space such that the second model is enclosedby the wet composition; solidifying the wet composition, pores beingestablished in the solidified wet composition; allocating a function ofa second tool part to the solidified material, wherein the second toolpart can cooperate with the first tool part and wherein a seconddelimitation surface of the molding space is formed by an upper surfaceof the second model; separating the first tool part and the second toolpart; removing the second model; bring together the first tool part andthe second tool part; introducing into the molding space a material forforming the dental product; and hardening the material for forming thedental product, wherein heat removal from the material for forming thedental product is effected by the heat-conducting particles, wherein gastrapped in the material for forming the dental product is conducted awayby the pores established in the solidified wet composition, and whereinbreaking of the product is prevented by well balancing the porosity ofthe solidified wet composition and a flexibility of the material forforming the dental product after solidification of the material.
 2. Themethod according to claim 1, wherein the product is ceramic and/ormetallic.
 3. The method according to claim 1, wherein the material forforming the product is introduced into the molding space by injection orsqueezing.
 4. A device including an injection molding tool for use onceor a few times for producing a sinterable ceramic and/or metallicproduct, said device comprising:at least one first tool part; at leastone second tool part combinable with said at least one first tool partto form a molding space for said product, said at least one second toolpart being made of a readily worked and form-stable material, containingpores and admixed heat-conducting particles and being produced using awet composition; a wet composition-enclosing member that can engage theat least one first tool part during production of the at least onesecond tool part; and a unit that can be connected to the at least onesecond tool part and can be arranged with the at least one first toolpart for absorbing internal lateral displacement forces arising duringsqueezing or injection of an injection molding composition; wherein saidinjection molding tool is adapted to receive an injection moldingcomposition containing a ceramic and/or metallic powder that isintroduced into the injection molding tool with low or medium pressurefor forming the product; and wherein said pores and said admixedheat-conducting particles conduct away heat generated during molding andgas trapped in the molding space, said pores also provide awell-balanced porosity for effecting conduction of the gas and, togetherwith a flexibility in the injection molding composition as solidified,permit the product to be separated from the at least one first tool partand the at least one second tool part without braking.
 5. The deviceaccording to claim 4, wherein the injection molding composition assolidified has a modulus of elasticity of greater than 1 GPa.
 6. Thedevice according to claim 4, wherein the heat-conducting particlescomprise aluminum or aluminum alloy particles.
 7. The device accordingto claim 6, wherein the heat-conducting particles comprise 30% to 80% byvolume of the wet composition.
 8. The device according to claim 6,wherein the heat-conducting particles comprise 20% to 40% by volume ofthe wet composition.
 9. The device according to claim 4, wherein theheat-conducting particles comprise 30% to 80% by volume of the wetcomposition.
 10. The device according to claim 4, wherein theheat-conducting particles comprise about 20% to about 40% by volume ofthe wet composition.
 11. The device according to claim 4, wherein theheat-conducting particles establish an effective heat-removal network inthe injection molding composition as solidified.
 12. The deviceaccording to claim 4, wherein a porosity of the injection moldingcomposition as solidified is 5% to 50% by volume.
 13. The deviceaccording to claim 4, wherein a porosity of the injection moldingcomposition as solidified is about 30% by volume.
 14. The deviceaccording to claim 4, wherein a porosity of the injection moldingcomposition as solidified effectively removes air existing in connectionwith molding of the product.
 15. The device according to claim 4,wherein the readily worked and form-stable material comprises plaster,cement, or presintered ceramic powder.
 16. The device according to claim4, wherein the device produces a dental product.
 17. The deviceaccording to claim 16, wherein the dental product is a dental bridgeshell or dental prosthesis.
 18. The device according to claim 4, whereinthe wet composition is liquid or viscous at room temperature and whereincrystal formation or chemical reaction in the wet injection moldingcomposition begins during mixing of the wet composition.
 19. Aninjection molding tool for producing a product, the tool comprising:afirst tool part; a second tool part mutually combinable and separablefrom the first tool part, the first tool part and the second tool partdefining a molding space for a shell for receiving an injection moldingcomposition when combined, the second tool part being formed from asolidified wet composition including pores and heat-conductingparticles, the pores conducting away gas from the molding compositionand help to prevent breaking the molding composition upon solidificationand separation from the second tool part, and the heat-conductingparticles removing heat during introduction of the molding compositioninto the molding tool; a first model of a base supported by the firsttool part such that an upper surface of the first model forms a firstdelimitation surface for the molding space; a second model correspondingto a shape of the shell for application to the first model, the secondtool part being formed by applying the wet composition at least aroundand enclosing the second model when the second model is positioned onthe first model, wherein the second model is removable from the firstmodel to form the molding space.
 20. The tool according to claim 19,wherein the product is a shell for a ceramic and/or metallic productand/or ceramic and/or metallic prosthesis that can be anchored to abase.